1. Field of the Invention
The present invention relates to radio receiver devices and decoding methods therefor, and more particularly to a radio receiver having test modes which reduce the time to measure the performance of the device in the production environment.
2. Description of the Prior Art
With the advent of radio receivers for receiving data and microprocessor based decoders, receiver performance testing methods have substantially changed. Presently, in most cases it takes more time to measure the performance of a data receiver than it takes to measure the performance of an equivalent audio receiver in the receiver production environment. Basic reasons for this problem is that digital decoders operate on the same decoding format in production as is used in the field, the field page rate being relatively slow for a selected receiver.
One coding system which utilizes a binary data format is illustrated in FIGS. 1A through 1D. An encoder such as a Motorola Model Z6VEN may be used to generate the aforesaid 15-group, synchronous paging format. With such a system it should be noted that the transmitter is on all the time and would generate a null code if a specific generation of a group and address code is not required. The data is transmitted at predefined times in a fixed data structure at a rate of 200 bits per second. The transmitted data stream is organized into a hierarchy of fields. These fields are: synchronization, group, and address as illustrated in FIGS. 1B, 1C and 1D, respectively.
Referring to FIGS. 1A and 1B it can be seen that the coding format is divided into 15, 9-word groups. The groups occupy fixed positions within the overall data structure and are not necessarily transmitted in a consecutive number sequence; however, each of the 15 groups is transmitted just once every system cycle.
As seen in FIG. 1B, a group consists of one synchronization word and 8 address words. Each word contains 31 bits of information. The format of a synchronization word is different from that of an address.
The synchronization word prefaces each group. Referring to FIG. 1C, this word is assembled from 3 distinct fields, namely: bit sync, frame sync, and group ID. The bit sync field consists of 9 bits of alternating 1's and 0's, starting with a leading 0. This field is used to obtain and maintain decoder synchronization with the incomming data stream. Because of the tight system on relative clock frequency skew, clock acquisition and adjustment consists of phase correction only between the decoder and the transmitter clocks.
Still referring to FIG. lC the bit sync field is followed by a 15-bit framing field. This field contains a predefined, pseudo-random binary sequence, which is used to define word boundaries within each group. On a long-term basis, it is also used to check the integrity of the recovered data.
The final field comprising the synchronization word is the group ID. This field identifies to which of the 15 possible groups that the next 8 addresses belong. Since the group ID field position is fixed, it functions much like the frame field. During initial synchronization, the group ID field is used to place the decoder into the correct group. It should be noted in this system that the group ID is transmitted once during each system cycle to allow the pager having the associated group code to synchronously sample just 9 consecutive words of the 135-word format to determine if it has been paged. During normal operation the group ID field also is used to check the data integrity period. The group ID is configured as a 7-bit code in a 7, 4 BCH format. No error correction is used.
Following the synchronization words are the 8 address words. Each address word is identical in format, differing only in information content a 31, 16 BCH code being used. Single error correction is permitted. The address data follows this format, unless no information is being sent in an address word. In this case, the 31 bits are replaced with alternating 1's and 0's, which are commonly referred to as the null code.
One radio paging device which responds to the above mentioned coding format is the RC-13B tone-only binary digital radio pager manufactured and sold under the trademark Pocket-Bell.TM..
In the "normal" mode (field mode) of operation, the aforesaid pager decodes one page every three system cycles. This is a page rate of one page every 62.775 seconds. In another test mode designated the "20 second" mode the system may decode one page for each system cycle which results in a page rate of one page every 20.925 seconds. Still another test mode designated the "group test" mode requires that the encoder format be modified so that it is always transmitting one group. The pager may decode one page, in every group. This results in a pager decoding rate of one page every 1.395 seconds. Still in another mode designated "S" mode the decoder of the paging device ignores the group identification information in a synchronization word and may decode one page in every group. This also results in a pager decoder rate of one page in every 1.395 seconds. Thus, the radio paging device may only decode and alert pages every 1.395 seconds. Thus, the standard 20 page production sensitivity measurement testing would take 27.9 seconds. This is because the decoder operation only allows the decoder to decode and alert the status of one of the eight addresses in the 1.395 second group.